title: Diabetes modifies effect of high-phosphate diet on fibroblast growth factor-23 in chronic kidney disease.
abstract: BACKGROUND
  The pathophysiology of calcium-phosphate disturbances in diabetic (DM) kidney disease differs from that in non-DM chronic kidney disease (CKD).
  
  
  OBJECTIVE
  We compared the effect of a 6-day high-phosphate diet on serum fibroblast growth factor-23 (FGF-23) and other parameters of calcium-phosphate metabolism in DM and non-DM CKD patients.
  
  
  METHODS
  This was a prospective interventional study in a research center setting. PARTICIPANTS, INTERVENTION, AND MEASURES: Twenty-six nondialysis patients with stages 3-5 CKD and albuminuria less than 300 mg/g creatinine were recruited from February 2011 to November 2012 (15 DM, 11 non-DM). All patients received a high-phosphate diet (1800 mg/d) for 6 days. At baseline, day 3, and day 7 serum FGF-23, PTH, Ca, P, 25-hydroxyvitamin D, 1,25 dihydroxyvitamin D, monocyte chemoattractant protein-1, and calcium and phosphate urine excretion were measured.
  
  
  RESULTS
  In DM CKD patients, serum calcium was lower on days 3 and 7 vs baseline (P < .01, respectively), and in non-DM patients, it was unchanged. Serum phosphorus increased significantly only in non-DM patients on days 3 and 7 vs baseline (P < 0.01, respectively). Serum PTH was higher in the DM group on day 7 vs baseline (P = .04). Plasma 25-hydroxyvitamin D, 1,25 dihydroxyvitamin D, and serum monocyte chemoattractant protein-1 were unchanged in both groups. Serum FGF-23 increased in DM patients, from baseline to day 3 (58.1 ± 52.7 and 91.6 ± 71.1 pg/mL, P = .001) but later tended to decrease. In non-DM patients, there was a steady increase of FGF-23 between baseline and day 7 (75 ± 84.3 to 176 ± 197 pg/mL, P = .04). Urine phosphate excretion was significantly higher on day 7 in DM patients only (P < .05).
  
  
  CONCLUSIONS
  PTH seems to play the major role in the regulation of phosphate excretion in DM CKD. The role of FGF-23 in phosphate disposal in DM CKD remains debatable.
authors.affiliation: University Hospital, Medical University of Lodz, Department of Nephrology, Hypertension, and Kidney Transplantation, Kopcinskiego 22, 90-153 Lodz, Poland. nefro@wp.pl.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Muras
authors.forename: Anna
authors.initials: A
authors.lastname: Masajtis-Zagajewska
authors.forename: Michał
authors.initials: M
authors.lastname: Nowicki
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood / Q000652:urine; D002118:Calcium / Q000097:blood / Q000652:urine; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D003928:Diabetic Nephropathies / Q000097:blood* / Q000503:physiopathology / Q000652:urine; D004032:Diet / Q000009:adverse effects*; D015536:Down-Regulation; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood / Q000378:metabolism; D010710:Phosphates / Q000009:adverse effects* / Q000652:urine; D010758:Phosphorus / Q000009:adverse effects / Q000097:blood; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000150:complications* / Q000503:physiopathology / Q000652:urine; D012720:Severity of Illness Index; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D015415:Biomarkers; C000717427:FGF23 protein, human; C470125:PTH protein, human; D010281:Parathyroid Hormone; D010710:Phosphates; D010758:Phosphorus; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002118:Calcium